Electrical switch



Sheets Shesi: 1

F. ALDENQQFEFF ELECTRICAL swmca Flled Maren 9. 192:;

April 12. 1927.

1 l Apnl 927 F. ALDENDORFF ELECTRICAL SWITCH Filed March e. 1925" 4 Sheets-Shet- 4 1 WOW Patented Age-n12, 1927.

UhlllEl) STATES 1.624,.202 caries.

FRITZ ALEEHT'OBFF, OF VTELMERSDORF, NEAR BERLIN, GERMANY.

ELECTRICAL SW'ITCF.

Application filed March 9, 1925, Serial No. 14,107, and in Germany March 11,1824.

This invention relates in general to .elec

tlical switches and more particularly to switches or selectors for electro-m-echanically controlled telephone systems.

An object of the invention is to provide aswitch of a high capacity which is capable of selecting a tree trunk from a large number of trunks in a very short time such as a traction of a second.

The switch in accordance with this invention is adapted to select a large group of trunks and then to hunt for a tree trunk in the selected group by means of brushes which are first rotated at a high .speed relatively to the selector shaft and thereupon the shaft and the brushes are rotated together at a lower speed until a tree trunk is found.

The feature and scope of the invention will be best understood from the following description and byre-ference to the drawing and appendent claims.

The invention is illustrated by way of example in the drawing in which Fig. 1 is a front View of the selector and Fig. 2 is a top view of the same.

Fig. 3 is a vertical section through a part or the select-or shaft on which the uncoupling magnet and the spring boxes are mounted.

Fig. at is a perspective View of the top bearing plate with the attached slide way for supporting the brush carrier.

Fig. 5 is a view of the brush carrier.

Fig. 6 is a top VlW 0t 5.

ig. T is a perspective view of the iron sheet body 011 the lifting magnet without the core and the armature.

F lg. 8 is a perspective view of the iron sheet body of the rotary magnet without the core and the armature but with the attached stroke limiting stop for the rotary pawl and the rotary pawl guide.

Fig. 9 shows the holding pawl for the steppingwheel with the catch that keeps the holding pawl out of engagement with the stepping" wheel during the baclrwaro rotary increment of the brush carrier.

10 shows the circuits used for the selector.

ank compris contact rows be precisely ad horizontal double lines 11, 12. Each set'ot contact rows is embedded in a bloclr ot insulating material, preferably in the sha not a semi-circle. Each semi-circular block is mounted between two arcuate iron 111cm here, as 13, 1%. The flat iron membersare fixed to the block of insulation by screws and 16. The arcuate members 13 and 1% have holes at their ends so that they may be threaded onto the lateral rods 1, 2 as shown in F igs. 1 and 2. The upper flatarcuate member oteach division 7., 8, 9, 10 otthe contact bank is fixed to the rods 1 and 2 by clamps 17 and 18. .The clamps 1T, 18.,each consist of two books and a connectingyolze, the latter having a threaded hole for the reception of a screw 19. Near the upper ends of the rods 1 and 2 is mounted the top bearplate 20 in which is journalled the .selector shaft. The plate 20 is fixed to the rods 1 and 2 by screw clamps inthe same way as the contact banks. The configuration of the top bearing plate 20 is illustrated most clearly in Figs. 2 and 1. At the rear the bearing plate 20 has two recesses 21, 22, which engage with circular grooves of screws 23, lhese screws are held by the topmost fiat arcuate iron members 13. By turning the screws the position of the bearing plate 20 with respect to the horizontal can 'usted' even after the screw clamps 25, 26 are screwed fast.

At the front the top bearing plate 20 is.

formed with a downwardly extending bar 27 to which the slid-sway 28 for the brush carrier 1s attached by screws 29 and 30.

' The slideway is shaped so as to almost com pletely surround the middle selector shaft The bottom bearing plate 30 ot the selector is also formed or flat metal and fixed to the rods 1 and 2 by screw clamps S1 and 32.

The lifting magnet 33 consists chiefly of an iron body with two parallel members connected by a yoke, one of the lateral parallel members being formed with two hooks 8 1, (Fig. 7) and the yolrebeing formed with a downwardly extending member 36 and an upwardly extending angular member 37. means of its hooks 3%., which embrace the rod, and by a niece of flat iron 38 that is lait against the hooks and pressed against them by screws 39 (Fig. 2), the screws 39 engaging "Female threads in the rod 2. The:

The magnet is lined to the rod 2 by.;

downwardly extending member 36 of the lifting magnet 88 carries the vertical holding pawl 40 that engages with the rack ll of the brush carrier and maintains the latter in whatever position it has been lifted to. The member 36 also supports the stroke limiting screw 42 which determines the stroke of the lifting pawl 48. The upwardly extending angular member 87 of the lifting magnet 33 receives a screw i l by which the tensionof the lifting spring to that exerts a pull on the lifting pawl 48 is adjusted.

The lifting pawl 41-3 is attached to the arm 46 of the armature 47 of the lifting magnet 33 and, in its normal position, is raised by the spring 45. hen the lifting magnet is energized the armature l? attracted and swung around its pivot 48, the arm l6 being thereby swung downward so as to expend the spring 4:5 and caused the lifting pawl. 43 to engage with the next lower tooth of the rack ll. \Vhe the lifting magnet is 'dceuergized the spring to pulls the pawl 4:3 and the rack 41 one step upwards and the holding pawl 4-0 simultaneously rides over a tooth of the rack and engages the next teeth so as to hold the rack in the position into which it has been raised. The rack ll forms a part of the brush carrier 51 that is made from a piece of sheet metal. The upper part of the b ush carrier has the shape of a rectangular frame provided with notches 52 in its right hand side. Beneath the part 52 the brush carrier is provided with an arm 53 whose end is formed in the shape of an eye adapted to embrace the middle shaft 29 of the selector. The rack has two further arms 55, 56 that is formed with two rearwardly bent flat eyes 57, 58. The rectangular frame is also formed with two rearwardly bent tlat eyes 59. 60. The eyes 57, 58, 59 and 69 are threaded onto a rod 61. whose lower threaded end is screwed into a coupling disk 62 and whose top end is fixed by a scrcwrlamp 63 to an arm or. The arm. 64: is lixed by a second screw-clamp with the middle shaft 29. .Vhen the lifting magnet armature 4:7 is oscillated by current impulses the arm -l6 raises the brush carrier step b step and the eyes 57. 58. 59 and 60 s id up on the rod 61 while the eye 5d .es up on the middle'shaft 29. The stroke of the oscillating arm 46 is determined by a stroke limiting or stroke determining stop 49. which preferably consists of a flat piece of hard rubber or the like lixed to the lateral. limb of the magnet 33 by two screws 50 and 51.. The top end of the middle shaft 29 ournalled in the bearing plate 29 and its bottom end rests on a ball 0 arranged in the ceutral hole of a hubbed disk 71 supported by the horizontal bearing plate 39. The middle shaft 29 carries the uncoupling magnet 72 and the coupling disk 62. The coupling magnet 7 2 has the form of a cored cylinder provided at the top with a neck Tet that has an internal thread which receives an externally threaded bush or tube 73. The threaded brush 73 is fixed to the shaft 29, as by soldering. The internally threaded neck 7% of the cylindrical magnet 72 is surrounded by a ring 75 of insulation in which are embedded two slip rings 76, 77. The magnet 72 is secured by the screw 78 and washer 7 9 at the height to which it is adjusted. Pivotally mounted so as to swing up and down between the magnet 72 and the disk 62 is the armature 80 whose horizontal pivot is carried by the disk 62. The armature 80 has a downwardly extending coupling member 81 that protrudes through a perforation in the disk 62 and is adapted to engage with various rectangular holes 82, 88 in the toothed wheel 84:.

Fixed to the disk 62 is a sleeve 85, which is surrounded by a sprin box 86. The disk 62, sleeve 85 and spring box 86 are all fixed on the middle shaft 29 by means of a screw 87. T 1e toothed wheel 84 is adapted to rotate around the sleeve 85 and carries a pin 88 to which one end of a spring 89 is fixed. The other end. of the spring is fixed to the middle hub of the spring box 86 and is thus also attached to the sleeve 85 and the shaft 29. As will appear from Fig. 2 a holding pawl 90 engages with the toothed wheel 84 which is adapted to be rotated by the rotating pawl 91 of the rotary magnet 92. When the wheel 84 is rotated while the armature 80 is attracted to uncouple the disk 62 from the wheel 84-, the spring of the spring box 86 is wound up as will be more fully explained hereinafter.

But if the toothed wheel 84: is rotated with t ie armature 80 otthe coupling u'iaguet 72 is detracted the shaft 29 with a ll the parts 72. 89, 62, 84k, 86 fixed to it is rotated; to-

ether with the brush carrier.

Arranged. a t the bottom end of the shaft 29 is a spring box 93 which fixed to the shaft by a screw 94. The one end of the spring is attached to the hub of the hubbed disk 71. and the other end is fixed to the pc ripheral wall of the spring box 9 3. Hence whenever the shaft 29 is r ited the spring 95 of the sprin box 93 1 wound up and this spring box serves to turn the shaft 29 loo lit).

with the brush carrier back into their rotary normal position after the selector has been used.

The rotary magnet 92 which ha: the recangular form illustrated in 8 is fixed to the left hand frame rod 2 by means of two hooks 96 97 and a plate and screw similar to the plate and screw 38, 39 (F 2) that secures the lifting magnet 33. T he armature 95 of the rotary magnet 92 is pro vided with a short rearwardly bent arm 96 which receives one end of a pivot 93. The

. spring 98. that presses against arearward extension of the pawl 91 and thus keeps the stepping pawl in engagement with the toothed wheel84. When the armature 95 is in its normal position its arm 94 is held by a spring 104 in a position in which the stepping pawl 91 abuts against a stop 102. The tension of the spring 104 an-be adjusted by screws 105, 106 by which a short beam 107 provided with a knife edge can 1 be set i into different oblique positions lVhen the stepping pawl 91 abuts upon the stop 102 the .wheel 84 is locked against inotion in the direction of the arrow. It is locked against this .motion by the holding pawl 90.

The stop 102 is integral. with a guidemember 108 (Fig. 8) that guides-the stepping pawl 91. The combined stop and guide member 100 is fixed by a screw 102 on-the cornerofthe magnet 92 as shown in F ig. lVhenthe armature 95 is oscillated thestepping pawl 91 is guided by the finger 103 so that it is first lifted away from the wheel 84 and then, on the return stroke of the armature due to the spring 104, engages with the next tooth of the wheel 84.

As will appear more clearly in Fi 9 the holding pawl 90 is pivoted by pivot screws 110 on a small plate 109. A- spring 113 whose one end is attached to an arm 122 of the plate 109 presses the top end of the pawl 90 against the stepping wheel 84. The plate 109 is fixed to the top limb of the magnet 92 by two screws 111, 112. The pawl 90 carries apin 116 which serves as a stop for a small catch 115 provided with a nose 118. The arm 115 is urged by a spring 114 against the pin 116. The holding pawl 90 has a projection 123 that lies in the path of a cam 124 fixed to the stepping wheel 84. hen the stepping wheel 84 is turned by the stepping magnet in the direction of the arrow into the position in which the cam 124 strikes against the projection 123 ofthe holding pawl 90 this latter is swung back so that its pin 116 is retained by the nose 118 of the catch 115. The holding pawl is then retained in this position until the catch is pressed down by a pin 125 on the wheel 84 in the manner hereinafter more fully described.

The brush carrier which consists partly of the rack 41 and partly of the-frame-like piece 51, carries four brushes 126,127, 128, 129. The top brush 129 is shown in plan VlQW in 2. Each brush is fixed between a small plate 180 and an angular member 181. The angular member upon which each brush is mounted is fixed to the brush carrier by. two screws 132,133. The holesin the angular members .131 are large enough to enable the-brushes to be adjustcdwith re spect toithe contact bank.

Current is conducted to the winding of the coupling magnet 72 by brushesltl t, 185 which engage the slip rings 136, 137.

The operation of the selector .will now be described: The brushes of theselector are first moved v rtically-by the lifting magnet 33 whose armature 47 oscillates the arm 46 and the lifting pawl 43 when current impulses are sent to the lifting magnet windino'. At each attraction ofithe armature the a n 48 is swung downwards andthe spring 45 expended. lit-each current interruption the spring lifts the arm 46 with the, pawl 48 that has engaged the next lower-tooth of the 1'ack41. The rack 41, and. hence the brush carrier with .its four brushes 126, 127, 128, 129, is thus raised step by step, the eyes 58, 57, 59,. gliding upon the rod (31 while the eye 54 glides up on the middle shaft 29. The holding pawl 40 engages each tooth of the rack 41 in succession and holds thisrack in whatever position it is raised. l'lach ot the brushes 126429 travels during this stepping movement from one contact row or level .tothe. next, untilithedesired contact row or level is reached. Then the uncouplin magnet 72 is energized to at-- tract its'armature and wit-hdrawthe couplingmember 81 from the stepping wheel 84, see Fig. 3. The spring 89 of the spring box 89 now turns this spring box and the sleeve 85together with the shaft 29 and the disk 62 and thebrusli carrier ol at a high speed until a group hunting brush reaches a bank contact that is not connected with the battery so that the coupling magnet- 72 is deenergizedin the manner hereinafter. more fully described. The armature 80 then drops down and its coupling member 1 is urged by a spring 140 very quickly into a perforation as 82 or 88 of the toothed wheel 84. Thetoot-hed wheel 84 is thus rev coupled with the disk 62 and hence with the shaft 29. Current impulses are now sent through the rotary magnet 92 so as to oscillate the armature 95 and its arm 94. The stepping pawl 91 then rotates the stepping wheel 84step by step'until a free line in the group of trunks that is marked idle is found as hereinafter more fully described.

At the end of theconversation the uncoupling magnets 72 is again energized to attract its armature 80 and thus uncouple the disk 62 from the stepping wheel 84. The spring 89 then operates again and turns the shaft 29 and disk 62 together with the brush carrier further around. It is to be noted that as soon as the brush carrier is turned out of its-normal rotary position a corresponding notch 52 of the brush carrier support.141 slides onto the slide way 28 whichlatter maintains the brush carrier in the member 143 after the brush carrier support 141 has left the slide way 28. As soon as the brush carrier support 141 leaves the slide way 28 the brush carrier drops down onto the disk 62. The rotary magnet 92 now receives further impulses and the stepping wheel 84 then rewinds the spring 89. VJ hen this spring is fully rewound the cam 124 strikes against the projection 123 of the holding pawl 90 and the latter is now held by the nose W 118 of the catch 115 out of engagement with the stepping wheel 84. The impulses through the rotary magnet 92 now seizes and the magnet 92 is kept energized so as to release the stepping wheel 84. At the same time the coupling magnet 72 is deenergized so that the disk 62 is coupled to the stepping wheel 84 by the coupling member 81 ot the armature 80. Now the spring 95 of. the spring box 93 operates to turn the shaft 29 i together with the toothed wheel 84, disk 62, magnet 72, brush carrier and its brushes back into their normal position in which the lifting pawl 43 and the holding pawl 40 reengages the rack 41.

Fig. 10 shows a circuit arrangement by which the switch is made to operate as a group selector. It will be assumed that the group selector has been seized for use by the brushes 200, 201, 202 of a first group selector and that this operation has resulted in a current flowing through the brush 202, test wire 203, off-normal contact 204, resistance 205 to the positive pole of the battery. By this current a test relay in the first group selectort not shown) is energized and the calling line is connected through to the dialing impulse relay 206. The relay 206 is energized and closes its contacts 207, 208, 209, while opening its contacts 210 and 211. At contact 207 the release relay circuit is closed, this circuit extending from the negative pole through 207, 212, resistance 213 to the positive pole. The relay 212 closes at its contact 214 a locking circuit for it self and at its contact 216 establishes a current path for the current flowing through the test wire 203 so as to maintain this (511 cuit after the contact 204 is opened as here inafter described. ing subscriber wishes to step the brushes 217, 218, 219, 220 up to the fourth contact row or level of the contact bank, the calling subscriber sends in five impulses, for his impulse transmitter or dial is arranged in accordance with the invention to always Assuming that the call-' send in an additional impulse: so that in the ance 223 to the positive pole. The relay 222- closes its contact 224 and opens contact 225. On the ensuing attraction of the impulse relay 226, a current now flows from the negative pole through contact 226 of relay 227, 209, 224, left winding of relay 221 to the positive pole so that relay 221 is energized and closes its contacts 228, 229, 230. At the next retraction of the impulse relay 206 the lifting magnet 33 receive the current that flows from the negative pole through 214, 221, 228, 33 to the positive pole. The nextthree numerical impulses cause three further lifting impulses to be sent over the same path through the lifting magnet 33 so that the brushes 217, 218, 219, 220 are lifted to the fourth level.

In the comparatively long interval in which the impulse relay 206 is kept continuously energized after the lifting impulses have been sent in the changeover relay 222 is kept short-circuited by contact 208 so that the changeover relay armature drops back. The uncoupling magnet 72 then receives a current impulse that flows from the negative pole thorugh 226, 209, 225, 72, 230, 231 to the positive pole. By this means the coupling disk 62, Figs. 1 and 3, is uncoupled from the stepping wheel 84 and the spring 89 now whirls the brushes round at a high speed. As soon as the brushes leave their normal rotary position the contacts 204 and 23 are opened by the disk 62, the contact 232 having been previously closed. It will be assumed that the first two groups comprising, say, ten trunks each in the level to which the brushes have been lifted are all engaged. The uncoupling magnet 32 will consequently receive current first through the chain of contacts 233 to 235, contact 232, 240 and then through the chain of contacts 236 to 238, contact strip 239, brush 220 and contact 240. Each contact of the said chains of contacts is associated with a trunk. Supsosing a trunk in the next group of trunks is free, the chain of contacts 242 to 244 will be open at the contact, say 243, of the free trunk and the positive pole of the battery will therefore be disconnected from the contact strip 241. When the brush 220 reaches the arcuate contact strip 241 whose length is such that it occupies as great an are as ten individual sets of bank contacts, the uncoupling magnet 72 is deenergized. Due to the length of the contact 241'the armature of the uncoupling magnet 72 is given suincient time to retract in spite of the high speed of the brushes and the coupling disk that rotates the brush carrier is coupled with the stepping wheel 84. The stepping wheel 84 arrests the brushes 217 to 220 in a position in which the brush 220 registers with the contact 245 and now the relay 246 is energized by current that flows from the negative pole through 226, '209, 225, uncoupling magnet 72, 240, 220, 245, right hand winding of relay 246 to the positive pole. The relay 246 is energized by this current and closes its contacts 247, 248, but the resistance of said relay winding prevents the coupling magnet 72 from being reenergized. By its contact 248 the relay 246 closes a locking circuit for itself which extends from the positive pole through its lefthand winding, 248, 214 to the negative pole and by its contact 247 the relay 246 closes the circuit of the relay 227. The relay 227 closes a circuit for the rotary stepping magnet 92 which extends from the negative pole through an interrupter 249, contact 250, 02, 251, 252 to the positive pole. The rotary magnet new steps the toothed wheel 84 and the disk 62 and theshar t 29 and the brushes stepby step and as soon as the brushes reach a free trunk in the trunk group to whichthe brushes whirled round the test relay 253 is energized in a known manner by 'a current that fiows from the negative pole through 254, 253, brush 219, bank'contact 255 to the next group selector ahead or to the connector. The'test relay 253 opens at its contact 252 the circuit or" the rotary magnet-'92. lVhen the test relay connects the talking wires256, 257 through to the next selector it also maintains the impulse relay 206 energized by its contact 258. At

the end of the connection the circuit of the test relay 253 is opened in a known manner and when the calling subscriber replaces his net 72 is now energized by a current flowing from the negative pole through contact 215, 72, 62, 261 to the positive pole and the spring in-the spring box 86 now rotates the brushes 217 to 220 further around until the projection 142, Figs. 1 and'2, strikes against the stop 143. The brush carrier with the brushes 217 to 220 now drops down. The deenergization of the test relay also results in the closure of the circuit of the rotary magnet 92 from the positive pole through 252, 251, 92, 250, 249 to the negative pole. As the uncoupling magnet-72 is still energized the stepping wheel 84 will now he stepped round by itself so as to wind up the spring of the spring box 86. When this spring is fully rewound the cam 124, Fig. 2 strikes against the projection 123, see Figs. 2 and 10, and swings back the holding pawl so that its pin 116 is caught by the nose 118. At the same inie the contact 261 is opened while the contact 262 is closed. Through the opening or contact 261 the coupling magnet and the relay 227 are deenergizcd, the latter having previously closed a locking circuit for itself that extended through its armature contact 264 and contact 261. kept energized by the current through contact 262 and the stepping wheel 84 is now released both from its holding and stepping pawls. The second spring box 93 nowrotates the shaft 29' with all the parts ass0- ciated with it, including the brushes, back into the normal rotary position. As soon this position is reached a pin 125 fixedin the stepping wheel 84- (see Fig. 2) presses down the catch 115 so that the pin 116 of the holding pawl 90 can slip back over the nose 118. The holding pawl 90 then reengages the stepping wheel 84 and the contact 262'is opened and deenergizes the rotary magnet 92. As the disk 62 has also reached its normal position the contacts 231 and 204 are now also reclosed and the selector'can now again be seized through the flowing of a test current over the test wire 203 and the resistance 205.

If the selector is seized by a calling subscriber but the impulse relay" 206 does not receive any dialing impulses on account of the calling subscriber abandoning theconnection, only the relays 212 and 222 will be energized for a moment due to the energization and the subsequent deenergizat'ion of the relay 206 and the lifting magnet andselee-tor will not be operated in any way;

I claim:

1. A switch comprising a series o'fgroups of trunk line terminals, brushes adapted to trail over said terminals, numerical means for effecting a cooperation of said brushes with a desired series of groups of trunk line terminals, a power device tor moving the brushes continuously at a high speed past all busy groups of trunks until a group in which there is a tree trunk is reached, nonnumerical means for controlling said power device, and means for rotating the brushes at a lower speed after the brushes have reached a trunk group in which there is a tree trunk.

2. A switch comprising a longitudinally immovable but rotatable shaft, a brush carrier, means for moving the brush carrier along said shaft, means for rotating the brush carrier relatively to said shaft, means for rotating the brush carrier together with said shaft, a series or" groups of sets of terminals,

and brushes on the brush carrier for selecting a said series and hunting tor a set of terminals in a group ot the selected series.

The rotary magnet '92 is now Hill Pix

3. A switch comprising series of groups of trunk line terminals, brushes adapted to trail over said terminals, numerical means for effecting a cooperation of said brushes with a desired series of groups of trunk line terminals, a spring for moving the brushes continuously at a high speed past all busy groups of trunks until a group in which there is a free trunk is reached, non-numerical means for controlling the power of said spring, and means for rotating the brushes at a lower speed after the brushes have reached a trunk group in which there is a free trunk.

4. A switch comprising a longitudinally immovable but rotatable shaft, a brush carrier, a lifting magnet for moving the brush carrier step by step along said shaft, a spring for rotating the brush carrier at a high speed relatively to said shaft, means for coupling the brush carrier with said shaft, a stepping magnet for rotating the brush carrier together with the shaft step by step, a series of groups of trunk line terminals, and brushes on the brush carrier for selecting a said series when the lifting magnet operates and for finding a free trunk in a said group after the spring has rotated the brush carrier and when said stepping magnet operates.

5. A switch comprising a longitudinally immovable but rotatable shaft, rows of contacts partly encircling said shaft, a brush carrier, a lifting magnet for stepping the brushes ofthe brush carrier up to any desired rows of said contacts, means for rotating said brushes at a high speed over said contact rows to any desired position, means for thereafter moving the brushes at a lower speed until they reach a desired individual set of bank contacts, and non-numerical means for controlling the rotary movement of said brushes.

6. In a switch, a longitudinally immovable but rotatable shaft, groups of bank contacts arranged around said shaft, a brush carrier, numerical means for stepping the brush carrier along said shaft, non-numerical means for rotating the brush carrier at a high speed until the brushes reach a bank contact group one of whose contacts belongs to a free line, means for coupling the brush carrier to the shaft when such a group of bank contacts is reached, and non-numerical means for stepping the shaft with the brush carrier over the bank contacts in said group until a free trunk in the group is found.

7. A group selector for an electromechanically controlled telephone system comprising a longitudinally immovable but rotatable shaft, a brush carrier with brushes adapted to be lifted and rotated relatively to said shaft non-numerical means for rotating the shaft and the brushes together, numerical means for controlling the lifting movement essence of said brushes, and series of groups of trunk line terminals over any series of which the brushes may travel.

8. A group selector for an electromechanically controlled telephone exchange comprising a shaft, series of groups of trunks connested to groups of bank contacts arranged around said shaft, a brush carrier with brushes adapted to be set onto a said series and rotated at a high speed relatively to said shaft until the brushes reach a group of trunks in which there is a free trunk or trunks, means for subsequently rotating the shaftand brush carrier together until a free trunk is found, numerical means for controlling the setting of said brushes onto a desired said series, and non-numerical means for controlling the rotation of said brushes.

9. A group selector for electromechanically controlledtelephone exchanges comprising a longitudinally immovable but rotatable shaft, a plurality of rows of bank contacts arranged around said shaft, groups of trunks connected to each row of bank contacts, a brush carrier, numerical means for moving the brush carrier with its brushes along said shaft until the brushes register with a said row of contacts, non-numerical means for rotating the brush carrier with the brushes at a high speed relatively to said shaft until a group of bank contacts is reached in which is one or more free trunks, and non-numerical means for then rotating the shaft an d the brush carrier together at a lower speed until the bank contacts of a free trunk are reached by the brushes.

10. In a group selector for electromechanically controlled telephone'eXchanges,a longitudinally immovable but rotatable shaft, rows of bank contacts arranged around said shaft, groups of trunks connected to each row of contacts,a brush carrier, a lifting magnet for shifting the brush carrier with its brushes step by step along said shaft until the brushes register with a set of bank contact rows, numerical means for controlling the operation of the lifting magnet, with a spring for rotating the brush carrier with its brushes at a high speed relatively to said shaft until a group of bank contact sets is reached one or more of which sets are connected to a free trunk, means for coupling the brush carrier with the said shaft when the brushes reach such as group of bankcontact sets, a rotary stepping magnet for stepping the brush carrier and the shaft until the brushes reach a bank contact set belonging to a tree trunk, and non-numerical means for controlling the rotary movement of the brush carrier.

11. A selector comprising a series of groups of trunk line terminals, a group test contact for each said group of terminals, a brush, a power device for moving the brush over said testcontacts, a magnet for applying said power continuously until a group of trunk line terminals is reached by the brush in which there is a tree trunk line terminal, a test circuit which includes said group test contacts and controls said magnet, and a stepping magnet for stepping the brush after it has executed its continuous rotary movement.

12. A selector comprising a series of groups of trunk line terminals, a group test contact for each said group of terminals, a brush, numerical means for setting said brush onto a desired said series, a power device for moving the brush over said testcontacts, a magnet for applying said power continuously until a group of trunk line terminals is reached by the brush in which there is a tree trunk line terminal, a test circuit which includes said group test contacts and controls said magnet, and a stepping magnet 2 for stepping the brush after it has executed its continuous rotary movement.

In testimony whereof I have aifixed my signature.

FRITZ ALDENDORFF. 

